“It’s also incompatible with Russian assurances that they do not want Mr Snowden to further damage U.S. interests.”

Carney also renewed a U.S. call on Russia to expel Snowden so that he could be returned to American soil to face trial for leaking U.S. national security secrets.

Snowden earlier told activists he wanted to claim asylum in Russia until he can travel on to Latin America, in his first encounter with the outside world since becoming marooned at a Moscow airport three weeks ago.